1. Field of the Invention
The present invention relates to a method for the measurement of current-voltage characteristic curves of solar panels.
The invention also concerns an apparatus for the measurement of current-voltage characteristic curves of solar panels.
2. Description of Related Art
In the quality control and product development of solar panels, it is mandatory to test the panels using standardized test methods. Herein, simulation test methods are the only feasible choice, because natural sunlight does not produce reproducible test conditions. Typically, the tests are carried out to study the current output capability of a solar panel at varying loads under constant illumination conditions.
One commonly used method of testing solar panels is to subject them to a continuous flux of artificial light corresponding to the intensity of natural sunlight. This method subjects the panels to substantial heating and, moreover, consumes a lot of energy from the light sources. Heating the panels causes problems in the standardized measurement procedure, because according to standards, the measurement should be carried out at 25.degree. C. Besides, it is difficult to provide a light source capable of producing illumination with an even intensity distribution.
The next step in evolving standards is represented by the pulsed-light test method in which the solar panels are subjected to a short-duration pulse of artificial sunlight illumination delivering an intensity pulse with a rectangular pulse waveform. Typically, the energy of such a light pulse is about 10 kJ. The duration of the light pulse is generally in the order of a few milliseconds. To produce such a large amount of light energy as a rectangular pulse requires high-output equipment, which becomes very expensive. Generation of a long-duration light pulse from a discharge lamp requires complicated power electronics because the level of illumination should be controllable. Further, the light source control must be designed for high-current switching with a low error margin, these requirements inevitably resulting in expensive apparatuses.